1. Field of the Invention
The present invention refers to a device for the transport of substrates through vacuum chambers, especially coating machines with a substrate carrier, on or at which the substrate may be arranged, wherein the substrate carrier has at least one guide rail which extends along at least one side of the substrate carrier.
2. Prior Art
From CH 691 680 A5 and DE 297 15 535 U1 is known a transport device for work pieces in a vacuum machine in which the substrate carriers may be arranged for, especially, flat and large-surface substrates, such as glass panes on a corresponding plate-like, disk-like or frame-like substrate carrier, with the substrate carrier having permanent magnets at its upper side that interact with a magnetically soft U-shaped holder, which is also fitted with magnets, such that the substrate carrier is transported at its upper side without contact. Disclosure of the aforementioned documents is fully incorporated into the present disclosure by way of reference.
Although this solution already yields very good results, the arrangement of the magnetic rail at the residual substrate carrier, for example a carrier plate or a frame arrangement, leads to the problem that, in the case of large-surface substrates having a substrate carrier of certain dimensions, due to the differential heating of the parts, namely magnet guide rail on one hand and carrier on the other, especially in the case of cyclical repetitive heating, which is often the case in coating machines, the parts of the substrate carrier rub against each other. Moreover, through the stresses and strains of the large-surface substrates or substrate carriers during transport, undefined deformation is introduced, such as torsion of the whole carrier, bending of the plates etc, which can lead to further relative movement of the magnet guide rail and the substrate carrier on one hand and, on the other, to frictional contact with and grinding or bumping at the magnetic holder in which the substrate carrier with its magnet guide rail is normally guided in the machine without contact, such that, in some circumstances, not unsubstantial wear may be generated that can disadvantageously impact on the quality of the coatings performed therein.